MPlotCookie Xpos.w,Ypos.w[,Colour] ; Plot a single pixel in the cookie to *represent* the [specified] colour

Plots a single pixel within the cookie of the currently used main chunky Shape to
/represent/ the specified colour or 0 in the Shape's graphic.  If the drawing
mode is set to MReMapMode or MSimpleReMapMode with the MDrawingMode command,
MColourMode will be used instead as it is illogical to try to perform remapping
to the cookie.